Coded centralized traffic control system



June 12,-1945. H. c. SIBLEY, JR 2,378,332 "CC iiiB CENTRALIZED TRAFFIC CONTROL SYSTEM I (Incl-neg w 5m d 530 B t L T E0 u m. tuna .n. hm m $55.3 E

Patented June 12, 1 945 CODED CENTRALIZE s D TRAFFIC YSTEM CONTROL Henry C. Sibley, Jr., Rochester, 'Y., assignor to General Railway Signal Company, Rochester,

Application July 29, 1944, Serial No. 547,174

5 Claims.

This invention relates to coded centralized traflic control systems, and more particularly to such systems used in connection with line wires connected by simplex coils at the ends for telegraph or the like. v Y

, In one type of a two-wirecoded centralized traffic. control system, such as disclosed for example in the application .of W. D. Hailes, et al., Ser. No. 484,728, filed April'27, 1943, the various field stations of the system perform their coding function by shunting the two line wires through a path of minimum resistance, with such filters as may be necessary if the line is also used for telephone communication. unshunted to the shunted condition of the line circuit produced by a field station is detectedfin the control office by the. change in current in an impulse transformer'connected to the line circuit,

prior application.

I In a code system of this shunt type, whenthe as shown and explained more in detail. in this A change from an able to use padding resistors in series with the simplex coils bridged across the line wires-at their ends, so as to maintain the desired margin between the shunted and unshunted condition of the line for satisfactory operation of the code ance of the telegraph system.

system. Such padding resistors increase the series resistance in the simplex telegraph circuit, and tend to interfere with its satisfactory operation. In other words, increasing the resistance of the simplex connections help the performance of the code C. T. C. system, but impairs the operation of the telegraph system. v

In view of these considerations, the. principal ,object of the present invention is to provide an improved circuit organization and arrangement of parts for a code centralized trafiic control com equivalent means in the line circuit so that its exciting current is that which flows to the portion of the linecircuit including the field stations of the C. T; C. system and only one simplex coil at the end of the line circuitremote from the control oifice. When the impulse transformer is thus connected into the line circuit, rather than in the manner disclosed in the Hailes, et al., application above mentioned, the change from the unshunted to the shunted condition of the line circuit causes a difference in current through the impulse transformer suitable for satisfactory operation with lower values ofthe padding resistors in series with the simplex coils, than if theimpulse transformer were energized by the current supplied to the padding resistor and simplex coils at both ends'of the line circuit, In order to maintain the desired balancefor the line circuit, "it is proposedlto divide the primary of the impulse transformer into two like windings of the samenumber' of turns and similar electrical characteristics, and include one of these primary windings in' each of the line wires. It

is also contemplated thatunder some conditions it maybe desirable or expedient to use-a larger paddingresistor at the end of the line circuit remote from the'control ofiice than at the other end of the control ofiice, so, as t o'help the operating margin between the shunted and unshunted condition ofthe line circuit, giving due consideration to the effect such inequality of the padding resistors' may 'have'upon'the perform- Various; other attributes, "characteristic" fea; tures,'and'advantages of the invention will be in part apparent,'and in part pointed out as the description progresses.

The accompanying drawing illustrates in a diagrammatic and conventional manner one specific form of the invention applied to one particular typeof code: communication system, such as disclosed in the application of Hailes, et al., Ser. No. 484,728, filed April 27,1943. The relays of the complete system more directly involved in connection with the present invention are illustrated and designated in this "drawing the same as in said prior application. 1

In the accompanying drawing, Fig. 1 illustratesthe general circuit organization and arrangement of parts in' a control office and at one field location insofar as necessary for an understanding of the present invention; and Fig. '2 is a simplified diagram of this same circuit organization.

Referring to the accompanying drawing, it is assumed that the same type of code communication system disclosed in the prior application of I-Iailes,et a1. above mentioned is to be applied to a line circuit which is s plexed for telegraph services or the like. 1 The telegraph equipment, indicated diagrammatically as TG, is connected in the usual way between ground and the midpoint of simplex coils SCI and SC2 at the ends of the line circuit comprising line wires LI, L2.

In order to obtain an adequate change in current when the line circuit is shunted, padding resistors RI and R2 are included in series with the simplex coils SCI and S02 at the ends of the line circuit in accordance with the usual practice. The values of these padding resistors RI and R2 are chosen with due regard to the various operating conditions, so as to obtain an adequate change in current through the impulse trans-' former without adding unnecessary series resistance into the telegraph circuit. In this connection, it can be seen that the series resistance in the telegraph circuit is not changed by an increase in the value of the padding resistors R2 at the far end of the line circuit, providing the other padding resistors RI for the near end are decreased a like amount, although the resistance balance of the two line wires to ground is changed by such unequal padding resistors at the ends. Under some conditions the effect of shunting the line wires is enhanced if the normal resistance of the padding resistors R2 across these line wires is large; and under such circumstancesit may be expedient to use a larger value for the padding resistors R2. than for BI, keeping the total resistance of RI and .R2 the same, and bearing in mind the effect of such resistance unbalance upon the performance and adjustment of the telegraph system. It should be understood that to the line wires LI, L2 is performed at each field station in accordance with its code call and the indications to be transmitted, by the operation of various relays including a bank of stepping relays, in the manner illustrated and described in detail in the prior application of Hailes, et a1. above mentioned. Considering the field start and referring to Fig. 1, if a change in the occupancy of a track section or the like should occur at a, field station which calls for transmission of some new indication to the control oflice, the energization of the relays 2E0 and 2L0 establishes a shunt across the line wires LI, L2

this invention contemplates either equal or unequal padding resistances at the ends of theline circuit, as may be best adapted to the operating conditions for a particular line circuit.

The control office equipment includes in part various relays CF, E, C, and the like for performing the functions explained in detail in the prior application of Hailes,. et a1. above mentioned; and for the purpose of understanding the nature .of the present invention, it is not necessary to consider sequence of operation of these various relays in detail, but merely point out certain .features ofthe operation.

Under the normal conditions shown, and while the code communicationsystem is at rest, the

battery CB in the control office is connected across the two line wires L1, L2 over a circuit path which may be traced from the lower line wire L2, through the coils 26,, 21 of the filter, back contact 25 of relay CF, front contact 24 of relay OR, back contact-23 of relay C, ballast lamps, battery CB, back contact 31 of relay C, back con tact .32 of relay CF, and coils 33 and 34 of the filter to the other upper line wire LI.

Since this invention has to do with the performance of the system when transmitting indications from field stations, it is unnecessary to consider the operating conditions for transmission of controls from the control oflice to a selected field station, itbeing sufficient to understand and appreciate that the line wires are maintained energized by the control oflice battery CB, and the field stations create a start pulse and create the desired coding by applying and removing a shunt to the line wires.

After the system has been set into operation.

by a start impulse from a field station, and while indications are being transmitted, the battery C13 is connected across the line wires L1, L2 by a circuit similar to the one just described, except that the relay CF is energized, and a circuit connection of the opposite polarity is made through its front contacts 25 and 32.

,The function of applying and removing a shunt over a circuit path which may be traced from the lower line wire L2, coils 35, 3B of the filter, front contact 48 of relay 2L0, front contact 354 of relay 2EO, back contact 355 of relay 2EE, and through coils 4I, .4201? the filter to the upper line wire LI. The energization of the relay ZEE removes this shunt by opening its back contact .355- The operation of these relays 2E0 and ZEE, with the relay 2L0 energized for an indication cycle, governed by the associated operation of the stepping relays and other elements of the field equipment, provides for shunting and unshunting the line circuit to provide short or long code elements during the successive time intervals of an indication.

It is an operating characteristic of their code system, to which the present invention more particularly relates, that shunts across the two line wires LI, L2 are intermittently applied and removed; and it can be appreciated that this causes a, change in the intensity of current supplied from the control ofiice battery CB to the line circuit, the current being increased above normal upon application of a shunt, and being restored to normal upon removal of the shunt. Such change in line current is detected by an impulse transformer; and the present invention relates to the way in which this impulse transformer is associated with a simplexed line circuit.

Referring to the drawings, two primaries 4 for this impulse transformer IM having the same number of turns are included in the line wire LI, L2 [between the point .5 at which the control oflice battery C13 is connected to the line circuit through the filter, and the end of the line remote from the control oifice and including the padding resistors R2, as clearly shown in the drawing. The secondary 6 of the impulse transformer IM is connected through pole change contacts I, 8 of the relay CF to the winding of an impulse relay F of the polarized magnetic stick type, the upper winding of this relay F being connected directly to one terminal of this secondary 5, and through back contacts 351, 358 and 359 of relays LV, C, and SC, and the front contact I of relay" CF to the other terminal of this secondary.

The change in current through the two primaries 4 of the impulse transformer IM, produced by the shunting and unshunting the line circuit, induces momentary voltages in the secondary 6 of this transformer to operate the polar contacts of relay F back and forth, in a manner more fully described in the application of Hailes, et al. above mentioned.

In the type of system disclosed in the prior application of Hailes, et a1. above mentioned, the energization of the relay F in the control office by a change in current produced by shunting the line circuit under normal conditions is emto properly condition thefield stations for reasons fully disclosed in said application of Hailes, et'al., the relay CF inthe control oflice is energized to change the polarity of energization of the line circuit from the control office battery CB.

' pole-change the connection between the secondary B of the impulse transformer IM and the relay F, when the relay -CF is energized at the beginning of'an indication cycle and changes the direction of current in the primaries 4 of said impulse transformer.

Considering the characteristics of the present invention, and referring to the simplified diagram of Fig. 2, it can be seen that the current through the two primary windings 4 of the impulse transformer IM flows over the line wires 7 LI, L2 past the various field stations to the end remote from the control office where the padding resistors R2 are connected across the line wires series with the simplex coils $02. In other -words, the primaries 4 of the impulse transformer IM are included in the line wires rather than in the battery connection across the line wires, and the current normally flowing in these primaries 4 corresponds with that supplied to the portion of the line circuit to which the field stations are connected, and to only one of the simplex connections at the remote end ,of the line. circuit, rather than the current supplied to both of the simplex connections. Consequently, when a field station shunts the line circuit, there is a greater change of current through the impulse transformer IM than would occur if this transformer were connected in series with the control office battery across'the line circuit, as shown in the prior application of Hailes, et al. above mentioned. This may be explained on the basis that a shunt applied to the line circuit at a field station changes the current in Y the portion of the line circuit connected with the field stations nearly as much as the total current from the battery is changed, while the normal current in this portion of the line circuit when the line circuit is unshunted is only about half of the total current from the battery.

This important characteristic of the invention makes it possible to obtain the desired current changes for satisfactory operation of a system of the character under consideration with padding resistors of lower resistance than would otherwise be required, thereby giving less objectionable afiect upon the telegraph system. As previously noted, if desired and conditions justify, the padding resistors R2 may be larger than RI.

It should be noted that the impulse trans former IM is constructed with two primaries 4' as near alike as practicable which are included separately in two line wires Ll, L2, in order to keep the line circuit balanced and minimize interference with the other facilities on these line wires.

The particular construction and arrangement of parts shown and described merely represents one typical specific embodiment of the invention; and I desire 'to have it understood that various modifications, adaptions and additions may be made in this particular construction and arrangement of parts without departing from the invention.

What I claim is:

1. In a code communication system for transmitting controls and indications between a control ofiice and a plurality of field stations over a pair of line wires simplexed for telegraph or the like, means for applying a potential across the line wires at the control office, means associated with each field station for intermittently shunting the line for transmission of code elements to the control office, and means in the control oflice including an impulse transformer'for detecting a change in the line circuit current supplied to the portion of the line circuit including said field stations and one of the simplex connections independently of the flow of current through the othersimplex connection.

2. In a code communication system of the character described for centralized trafiic control on railroads, a line circuit extending from a control office to a plurality of field stations and having simplex connections at the ends, a source of current at the control of'fice connected across said line circuit, means associated with each of the field stations for intermittently shunting said line circuit for transmission of code elements I to the control office, and means including a coil in said line circuit for detecting a change in line current supplied to the portion of the line circuit including said field stations and only one of the simplex connections when one of said field stations acts to shunt that portion of theline circuit.

3. In a code communication system for railroads, a two-Wire line circuit extending from a control oflice to a plurality of field stations,

means for supplying a steady potential across said line circuit at the control office, code transmitting-means associated with each field station for shunting said line circuit at different times in accordance with a code to be transmitted from that station to the control oflice, an impulse transformer in the control office having two like primary windings included one in each of said line Wires, and a polarized indication relay of the magnetic stick type connected to the secondary of said impulse transformer.

4. In a code communication system of' the character described for railways, aline circuit including two line wires extending from a control ofiice to a plurality of field stations, simplex coils at the ends of said line circuit, padding resistors in series with said simplex coils, said the control oflice.

5. In a code communication system of the character described for centralized traific control on railroads, a'pair of line wires simplexed for telegraph or the like extending from a control office to a plurality of field stations, means for supplying a steady potential across said line wires at the control oifice of one polarity under normal conditions and of the opposite polarity during an indication cycle, an impulse transformer including primary coils connected in said line Wires between the point of energization thereof and the portion associated with said field stations, a polarized relay connected to the secondary of said impulse transformer, and means for pole-changing the connection between said relay and the secondary of said impulse trans- 

